In ultrasound diagnostics, presence of tumors or presence of malignant tumors such as a cancer is diagnosed by measuring the hardness or softness of tissues in an object to be examined. In concrete terms, pressure is applied to biological tissues, displacement in each area of the object caused by the pressure is measured, elasticity information such as strain or elasticity modulus of each area is calculated based on the measured displacement, and the calculated elasticity information is imaged to be provided for diagnosis.
As a method for adding pressure to the object, it is common to apply an ultrasonic transmission/reception surface of an ultrasonic probe to the target tissues in the object manually or mechanically. Instead of pressing an ultrasonic probe manually on the skin surface of an object, a pressing device of a transrectal ultrasonic probe to be used by inserting into a body cavity for diagnosis of a prostate gland, etc. is proposed in Patent Document 1 and Patent Document 2.    Patent Document 1: US Patent No. 2002/0068870A1    Patent Document 2: WO2006/041050A1